1. Technical Field
The present invention relates to an electrophoretic sheet, an electrophoresis apparatus, a method for manufacturing an electrophoresis apparatus and an electronic device.
2. Related Art
It is generally known that, if electric fields are allowed to act on a dispersion system in which fine particles are dispersed in liquid, the fine particles move (or migrate) through the liquid under the influence of a coulomb force. This phenomenon is referred to as electrophoresis. In recent years, an electrophoresis apparatus that displays desired information (images) using the electrophoresis draws attention as a new display apparatus.
The electrophoresis apparatus is characterized by exhibiting display memory characteristics even at the time of stoppage of voltage application, possessing a broad viewing angle and having a capability to perform high contrast display with reduced electricity consumption.
The electrophoresis apparatus is a reflection type display that uses natural light as a light source. In the electrophoresis apparatus, titania particles are often used as white particles. Polyethylene terephthalate as a conductive transparent resin (hereinafter simply referred to as “PET”) on which indium tin oxide (hereinafter simply referred to as “ITO”) is vapor-deposited is often used to a substrate provided on a display surface side of the electrophoresis apparatus.
As the electrophoresis apparatus noted above, there is known a microcapsule type electrophoresis apparatus that includes a pair of substrates each having an electrode, a plurality of microcapsules arranged between the substrates and filled with electrophoretic particles and a liquid-phase dispersion medium, and a binder arranged between the substrates for binding the respective substrates and the microcapsules together.
JP-A-2005-84267 discloses an electrophoresis apparatus manufactured by supplying microcapsule dispersion liquid, which contains a plurality of microcapsules, a binder and a dispersion medium, to one of substrates and then supplying the microcapsule dispersion liquid once again to fill gaps between the microcapsules.
Meanwhile, a high reflectance of a white color and whiteness, i.e., a capability of reflecting light over an entire visible light region, are sought in the electrophoresis apparatus. However, a contrast of the conventional electrophoresis apparatus is not so great but merely about six. Furthermore, a reflectance of a white color is not greater than 35%, meaning that the white color is gray in a practical sense. For this reason, a color is not really acknowledged as a problem in the prior art.
Since a PET-ITO substrate generally used in a electrophoresis apparatus reduces light transmittance on the low wavelength side of a visible light region, it is sometimes a case that white particles look yellow-reddish.
In addition, it is sometimes a case that titanium oxide (titania) used as white particles becomes yellowish over time or has a yellowish color intrinsically. For this reason, the combined use of a PET-ITO substrate and titanium oxide as white particles in producing an electrophoresis apparatus reduces whiteness in display, which entails a problem of reducing a white and black contrast and a sharpness of an image.